Optical disk devices are a medium for storing large quantities of computer prepared data. When several optical disk drives are grouped together in a library system very large amounts of data are available to the computing system. However, if an optical disk drive fails, a replacement drive must either be available, or a special service call must be placed. Studies have shown that one of the major causes of failure for optical disk drives is failure of the semiconductor laser diode which produces a laser beam to read and write data on the optical media. The conventional method for detecting the approach of laser end-of-life is to monitor the operating current. If the current required to maintain a given operating point changes by a certain percentage the end-of-life is flagged. Such a conventional method cannot be used in a drive that does not have nonvolatile memory.
U.S. Pat. No. 5,019,769 describes an approach to predicting laser diode end-of-life by recording the operating characteristics of the laser in nonvolatile memory, analyzing changes in those characteristics, and generating a failure warning message when those changes match predefined failure prediction criteria.
Without nonvolatile memory, once the drive is disconnected from its power source the machine will lose its ability to recall previous current settings. Therefore, it is the general object of this invention to provide apparatus for determining when a laser is about to fail based upon the characteristics of the laser itself, obviating the need to utilize nonvolatile memory.